Milo g



(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

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wire 5 wve-mtoz A NTTED STATES PATENT FFICEL MILO G. KELLOGG, OFCHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SWITGHBOARD AND SUPPLYCOMPANY, OF SAME PLACE.

M U LTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,314, dated. October26, 1897.

Application filed November 29,1889. Serial No. 332,017. (No model.)

To (2 whom it may concern.

Be it known that I, MILO G. KELLOGG, of Chicago,Illinois,temporarilyresiding at Stuttgart, in theEmpire of Germany, have invented certainnew and useful Improvements in Multi ple Switchboards forTelephone-Exchanges, of which the following is a full, clear, concise,and exact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to a metallic-circuit telephone-exchange; and itconsists of a system of calling, switching, and testing such lines todetermine Whether they are in use.

In the accompanying drawings, illustrating my invention, Figure 1 is adiagram illustrating the main-line central-office switching apparatusand circuits. Fig. 2 shows a diagram of a subscribers-station apparatusand circuits necessary to illustrate my invention. Fig. 3 is a diagramof the operators cord system for receiving and answering calls andclearing out subscribers lines. an operators test system.

In Fig. 1, A is a sectional View of a section of one switchboard, and Ais a'sectional view of a section of another switchboard to which thesame lines are connected. I place as many boards in the central officeas are found necessary or desirable in order to answer the calls andmake the necessary connections. On each board is a spring-jack orsimilar switch for each line. Each switch has a contact-spring whichnormally bears on an insulated contactpoint and has a thirdcontact-piece insulated from the rest (except by the circuitconnections) and is adapted to receive a switch-plug and, when a plug isinserted, to disconnect the spring from the contact-point (on which itnormally bears) and connect the two contactpieces of the plug with thecontact-sprin g and said insulated contact-piece, respectively. In thefigures, g 9 represent the contact-springs of the different switches, hh the contact points on which the springs normally rest, and jj theinsulated contact-pieces of the switches. Z- Z are the switch-holes. a aare the rubber strips on which the switch parts are mounted, as shown,and through the fronts of which are the switch-holesl I. These holes areadapted Fig. 4 shows to receive the switch-plugs, (shown in Fig. 3 andmarked D D,) and when a plug is inserted into a switch it operates it,as above described. The insulated contact-pieces j j should be so placedthat a test-plug or similar device may be applied to them. 10 and a: arecallingannunciators.

The connection of each main line to the central-office switchboards andapparatus is as follows: One of the branches of the linesay Wire a, asindicatedis connected to all the contact-pieces jj of the switches ofthe line. The other branch of the linesay wire 12- passes successivelythrough the pairs of contact-points of its switches, which are normallyin contact, passing in each case to the spring first, as indicated. Thiswire, after passing from the last contact-point of the switch connectedfarthest from the subscribers station, is connected by a circuit-wire towire a of the subscribers line. In this circuit-wire thus connecting thetwo branches of the line is the line-annunciator.

In the subscribefs-station apparatus shown in Fig. 2, 1 is thecalling-generator. 2 is the signal-bell. 3 is the transmitter. dis theprimary, and 5 is the secondary, of the induction-coil. 6 is thetransmitter-battery. 7 is the telephone-switch,and 8 is thehand-telephone. The circuits andcontact-points are substantially asshown. The generator has an auto matic device with contact-points asshown,

constructed to remove the shunt from the armature-coil and connecttogether the two branches of the line when the generator is beingoperated. These two branches are otherwise open to each other at thesubscribers station when his telephone is on its switch.

The automatic device shown is a modification of a device very generallyused in magneto-generators for telephone calls. The modificationconsists, essentially, in the contacts and arrangement of circuits. Thehub of the driving-wheel of the generator has a V-shaped attachmentwhich engages with a pin in the crank or driving shaft. The spring I?normally, or when the generator is not in operation, presses againstthepoint 0. When the generatoris being operated,the pin,acting on theV-shaped arrangement, presses the driving-wheel toward thegenerator-magnets, and that carries the spring 19 away from point 0 andinto contact with point 01.

e is a contact-spring which remains in contact with an insulated pieceon the armature.- shaft, to which one end of the armature-coil isconnected. The otherend of the coil and also spring I) are connected tothe frame of the generator. The circuit of one side or branch of theline (marked 1)) is to the frame of the generator. nected through thesubscribers-station battery6 to the lever of the telephone-switch 7. Thecircuit-wire which connects the battery with spring eis connected topoint 0 and also through the transmitter 3 and the primary 4; of theinduction-coil to one of the upper contact-points of the switch. Theother side or branch of the line (marked a) is connected to point (1 andalso through the secondary 5 of the induction-coil and the telephone tothe other upper contact-point of the switch. The lower point of theswitch is connected through the signal-receiving bell 2 to the ground.

It will be seen from the description above given and the drawings thatwhen the subscribers telephone is on the switch and the generator is notbeing operated the two sides or branches of the line are open to eachother at the subscribers station. The generator is in circuit with wireI), but is shunted or shortcircuited, and wire bis grounded through thebattery and signal-receiving bell; also, that when the generator isbeing operated the short circuit is opened and the two sides or branchesof the line are closed to each other; also, that when the telephone isremoved from the switch the ground connection through the bell is open,the two sides or branches of the line are closed to each other and thetelephone and secondary of the induction-coil are in their circuit andthe primary of the induction coil, the

battery, and the transmitter are in a closed circuit with each other.

The transmitter-battery should be so placed in the apparatus that it isin circuit with wire b when the subscribers telephone is on the switch,and it may be in circuit with it all the time.

Fig. 3 shows an operators cord system with one pair of loop-switch plugsand their double cords, looping-in switch, and clearing-out annunciatorsand her telephone and callinggenerator and circuits. D D are theswitchplugs. n W. are their rubber insulations. m m are theircontact-pieces, and 0 is a metal strip on which the plugs normally restand which then connects the two contact-pieces of the plug. Gis a groundconnection. The method of operating the system in connection with theother apparatus will be apparent to those skilled in the art.

The operators test system (shown in Fig.

1 4) consists, essentially, of a wire grounded on one side, (at G,) withatest receiving instrument 1. in its circuit, and connected on its otherend to a flexible conducting-cord, to

Contact-spring e is conwhich is attached a test-plug T, adapted, at Vthe will of the operator, to be brought into connection with any switchcontact-piece j at her board.

Each operator has one cord system (with as many pairs of cords as shemay require) and one test system, and they should be so placed andconnected at her board that she may readily perform the operationsrequired of her.

It will be observed that in the operation of the system asubscriber, onoperating his generator, sends a current through a closed circuit,inwhich is his line-annunciator; also that when a line is switched at thecentral office its annunciator is cutout of its circuit.

When an operator makes a test of a line, by placing her test-plug on acontact-point j of a switch of the line and the line is not switched atany board and the subscribers telephone is on its switch, a completecircuit is established, in which is the test receiving instrument andthe subscribers transmitterbattery, and the instrument will sound,indicating that the line is free. is from the subscribers ground throughhis switch contact-points to his battery; thence through his battery andline and the several pairs of contact-points of its switches tocontact-piece j, to which the test-plug is applied, and thence to groundthrough the test receiving instrument. If, however, when a test is madethe line is in use, either by its being switched at some board and apair of its switch-points being opened or by the subscribers telephonebeing oif its switch, there will be no complete circuit established andthe instrument will not sound. The operator will therefore know thateither the line is switched for use at the central office or that thesubscribers telephone is switched for use, and she will not connect tothe line.

In multiple-switchboard systems an operator to whom certain lines areassigned to answer frequently receives several annunciator calls atpractically the same time, and it may require some time before she canswitch to a certain line and answer its call. In systems in which thetest depends only on the switching of the line at some other boardanother operator may in the meantime test the line, and finding it totest free may switch it with another line and cause annoyance andconfusion to the subscriber. In my system this trouble is obviated,because as soon as the subscriber takes his telephone from its switchthe line will test busy whether or not it is switched at the centraloflice. Again, in systems of testing which dependonly on the subscriberstelephone being on and off the switch confusion frequently occurs fromthe fact that a subscriber places his telephone on his switch afterfinishing conversation without sending in' a clearing out signal and hisline will test free and be connected to when it is alreadyswitched atthe central office. Lines in this condition are technically called tiedThis circuit 7 up. In my system, again, this trouble is obviated,because the line will test busy until it is disconnected at the centraloffice whether or not the subscribers telephone is on its switch. Thesystem therefore combines the advantages and obviates the disadvantagesof both the general systems outlined above.

The battery should be so adjusted to the apparatus and circuits that thecurrent sent to a line when it is tested will not operate theannunciator or signal-bell. It should, however, be such as to operatethe test receiving instruments over the circuits described.

The test system would be equally operative if the subscribers batterywere placed in the ground wire or connection at the subscribers station.It would also be operative if the two branches of the line were notnormally open to each other at the subscribers station, the onlydifference being that the batteries would be in a closed circuit andthere would be a larger consumption of battery material.

I claim as my invention and desire to secure by Letters Patent- 1. In atelephone-exchange system, a metallic-circuit line normally (or when theline is not in use) with its two branches open to each other at thesubscribers station and one of them grounded at the subscribers stationwhen it is not switched for conversation and not otherwise and having asubscribers transmitter-battery in its circuit, and a switch at thecentral oflice containing a pair of contact-points normally in contactand a third contact-piece insulated from the rest (except by the circuitconnections) said branch of the line which is normally grounded at thesubscribers station and has a battery in its circuit passing throughsaid pair of contactpoints and thence connected to said thirdcontact-piece, in combination with a switchplug adapted to be insertedinto said switch and when inserted to disconnect the pair ofcontact-points which are normally in contact, and a test receivinginstrument grounded on one side and connected on its other side to atest plug or device adapted, at the will of the operator, to be broughtinto connection with said third contact-piece of the switch,substantially as set forth.

2. In a telephone-exchange system, a metallic-circuit telephone-linehaving its two branches normally open to each other and one of themnormally with the subscribers transmitter-battery in its circuit andgrounded at the subscribers station when it is not in use but nototherwise, and a switch at the central office containing a pair ofcontact-points normally in contact and a third contact-piece insulatedfrom the rest (except by the circuit connections), said branch of theline which is normally grounded at the subscribers station passingthrough said pair of contactpoints and thence connected to said thirdcontact-piece, in combination with a switch-plug adapted to be insertedinto said switch and when inserted to disconnect said pair ofcontact-points, and a test receiving instrument grounded on one side andconnected on its other side to a test plug or device adapted, at thewill of the operator, to be brought into connection with said thirdcontact-piece, sub stantially as set forth.

3. In a telephone-exchange system, a metallic-circuit line, the twobranches of which are normally open to each other and one of which isnormally grounded and has a transmitter-battery in its circuit at thesubscribers station, and a switch with contact-points to remove saidground connection and close the two branches of the line to each otherwhen the line is in use, in combination with a switch to open the closedcircuit of the line at the central oflice when the line. is in use, anda test receiving instrument grounded on one side and connected on itsother side to a switch testing plug or device, adapted, at the will ofthe operator, to be brought into connection with the line with thecontact-points of said office switch between the connection and thenormal ground of the line at the subscribers station, substantially asset forth.

4:. I11 a telephone-exchange system,multiple switchboards,metallic-circuit lines connected to the same, the two branches of whichare normally open to each other at the subscribers station and one ofwhich is normally grounded and has a transmitter-battery in its circuitat the subscribers station, and switches at each subscribers station,each with contact-points to disconnect the line from said groundconnection and close the two branches to each other when the line is inuse, in combination with test receiving instruments, one at each board,each instrument being grounded on one side and connected on its otherside to a test plug or device adapted, at the will of the operator, tobe brought into connection with that branch of any line which isnormally grounded at the subscribers station, substan tially as setforth.

5. In a telephone-exchange system,multiple switchboards,metallic-circuit lines connected to the same, each line being normally(or when not in use) with its two branches open to each other and one ofthem grounded and with a transmitter-battery in its circuit at thesubscribers station when it is not in use and not otherwise, andswitches, one on each board for each line, each switch containing a pairof contact-points normally in contact and a third contact-pieceinsulated from the rest (except by the circuit connections), said branchof the line which is normally grounded and has a battery in its circuitat the subscribers station passing, successively,throu gh the pairs ofcontact-points of the switches of the line which are normally in contactand thence being connected to said third contactpieces of the switches,in combination with switch-plugs adapted to be inserted into said Itaining normally, at the subscribers station,

a transmitter-battery and a pair of contact-' points normally closed butwhich are open when the subscribers telephone is switched for useto-open said test-circuit, and at the central office, switchcontact-points which open the circuit when the line is switched for usebut not otherwise, and a pair of contact points which are normally openand are closed by an operator on testing,in combination with a testreceiving instrument in said circuit, substantially as set forth.

7, A test-circuit for a subscribers line, containing at the subscribersstation, normally, a transmitter-battery and a pair of contact- -pointsnormally closed but which are open when the subscribers telephone isswitched for use to open said test-circuit, and, at the central oflice,a series of pairs of contactpoints norm ally closed,one pair on each ofseveral multiple boards, each pair open when the line is switched attheir board, and a pair of contact-points normally open and closed by anoperator on testing,in combination with a test receiving instrument insaid circuit, substantially as set forth.

8. A test-circuit for a subscribers line,containing, at the subscribersstation, normally, a transmitter-battery, and a pair of contactpointsnormally closed but which are open when the subscribers telephone isswitched for use to open said test-circuit, and, at the central oflice,switch contactpoints which open the circuit when the line is switchedfor use but not otherwise, in combination with a series of branch orderived circuits to said test-circuit, each containing a test receivinginstrument and a pair of contact-points normally open and closed by theoperator on testing, substantially as set forth.

9. A test-circuit for a subscribers line,con taining, at the subscribersstation, normally, a transmitter-battery, and a pair of contactpointsnormally closed but which are open when the subscribers telephone isswitched for use to open said test-circuit, and at the central oifice,aseries of pairs of contact-points normally closed, one pair on each ofseveral multiple boards, each pair open when the line is switched attheir board, inv combination with a series of branch or derived circuitsto said test-circuit, each containing a test receiving instrument and apair of contactpoints normally open and closed by the operator ontesting, substantially as set forth.

10. In a telephone-exchange system, multiple switchboards,metallic-circuit linesconnected to the same, each line being normally(or when not in use) with its two branches open to each other and one ofthem grounded and with a transmitter-battery in its circuit at thesubscribers station when it is not in use, switches, one at eachsubscribers station with contact-points to open such ground connectionand close the two sides or branches of the line to each other when thesubscribers telephone is switched for use, and switches, one on eachboard for each line, each switch containing a pair of contact-pointsnormally in contact and a third contact-piece insulated from the rest(except by the circuit connections), said branch of the line which isnormally grounded and has a battery in its cir cuit at the subscribersstation passing, successively, through the pairs of contact-points ofthe switches of the line which are normally in contact and thence beingconnected to said third contact-pieces of the switches, and said thirdcontact-pieces being connected to the other side or branch of the line,in combination with loop-switch plugs adapted to be inserted into saidswitches and when aplug is inserted into a,switch to disconnect the pairof contact-points of the. switch and connect the two contact-pieces ofthe plug, respectively, with said third contact-piece of the switch andwith that contact-piece of the pair which is then connected with thefirst-mentioned side or branch of the line, and test receivinginstruments, one at each board, each instrument being grounded on oneside and connect-ed on its other side to a test plug or device adapted,at the will of the operator, to

be brought into connection with any of said third contact-pieces at itsboard, substantially as set forth.

11. In a telephone-exchange system, multi- Q IIO in contact and a thirdcontact-piece insulated from the rest (except by the circuitconnections), said branch of the line which is normally grounded and hasa battery in its circuit at the subscribers station passing,successively, through the pairs of contact-points of the switches of theline which are normally in contact and thence being connected to saidthird contact-pieces of the switches, and said third contact-piecesbeing connected to the other side or branch of the line, in combinationwith pairs of loop-switch plugs, the two contact-pieces of each plugbeing connected with the two contact-pieces, respectively, of

its mate by flexible switch-conductors, and each plug adapted to beinserted into said switches at its board, and when a plug is insertedinto a switch to disconnect the pair of contact-points of the switch andconnect the two contact-pieces of the plug, respectively, with saidthird contact-piece of the switch and with that contact-piece of thepair which is then connected with the first-mentioned side or branch ofthe line, and test receiving instruments, one at each board,eachinstrument being grounded on one side and connected on its other side toa test plug or device adapted, at the will'of the operator, to bebrought into connection with any of said third contact-pieces at itsboard, substantially as set forth.

12. In a telephone-exchange system, Inu1tiple switchboards,metallic-circuit lines connected to the same, each line being normally(or when not in use) with its two branches open to each other and one ofthem grounded and having normally the subscribers transmitter-battery inits circuit, switches, one at each subscribers station withcontact-points to open such ground connection and close the two sides orbranches of the line to each other when the subscribers telephone isswitched for use, and switches, one on each board for each line, eachswitch containing a pair of con tact-points normally in contact and athird contact-piece insulated from the rest (except by the circuitconnections), said branch of the line which is normally grounded and hasa battery in its circuit at the subscribers station passing,successively, through the pairs of contact-points of the switches of theline which are normally in contact and thence being connected to saidthird contact-pieces of the switches, and said third contact-piecesbeing connected to the other side or branch of the line, in combinationwith loop-switch plugs adapted to be inserted into said switches andwhen a plug is inserted into a switch to disconnect the pair ofcontact-points of the switch and connect the two contact-pieces of theplug, respectively, with said third contactpiece of the switch and withthatcontact-piece of the pair which is then connected with thefirst-mentioned side or branch of the line, and test receivinginstruments, one at each board, each instrument being grounded on oneside and connected 011 its other side to atest plug or device adapted,at the will of the operator, to be brought into connection with any ofsaid third contact-pieces at its board, and a battery at the subscribersstation in the complete test-circuit thereby established, substantiallyas set forth.

13. In a telephone-exchange system, multiple switchboards,metallic-circuit lines con nected to the same, each line being normally(or when not in use) with its two branches open to each other, and oneof them grounded and having normally the subscribers transmitter-batteryin its circuit, switches, one at each subscribers station withcontact-points to open such ground connection and close the two sides orbranches of the line to each other when the subscribers telephone isswitched for use, and switches, one on each board for each line, eachswitch containing a pair of contact-points normally in contact and athird contact-piece insulated from the rest (except by the circuitconnections), said branch of the line which is normally grounded and hasa battery in its circuit at the subscribers station passing,successively, through the pairs of contact-points of the switches of theline which are normally in contact and thence being connected to saidthird contact-pieces of the switches, and said third contact-piecesbeing connected to the other side or branch of the line, in combinationwith pairs of loopswitch plugs, the two contact-pieces of each plug,being connected with the two contactpieces, respectively, of its mate byflexible switch-conductors, and each plug adapted to c be inserted intosaid switches at its board, and when a plug is inserted into a switch todisconnect the pair of contact-points of the switch and connect the twocontact-pieces of the plug, respectively, with said third contact-pieceof the switch and with that contact-piece of the pair which is thenconnected with the firstmentioned side or branch of the line, and testreceiving instruments,one at each board, each instrument being groundedon one side and connected on its other side to a test plug or device,adapted, at the will of the operator, to

be brought into connection with any of said third contact-pieces at itsboard, and a battery at the subscribers station in the completetest-circuit thereby established, sub stantially as set forth.

14. In a telephone-exchange system, multiple switchboards,metallic-circuit lines connected to the same, one side or branch of eachline being grounded, with a transmitter-battery in its circuit at thesubscribers station when it is not in use, switches, one at eachsubscribers station with contact-points to open such ground connectionand close the two sides or branches of the line to each other when thesubscribers telephone is switched for use, and switches, one on eachboard for each line, each switch containing a pair of contact-pointsnormallyin contact and a third eontact-piece insulated from the rest(except by the circuit connections), said branch of the line which isnormally grounded and has a battery in its circuit at the subscribersstation, passing, successively, through the pairs of contact-points ofthe switches of the line which are normally in contact and thence beingconnected to said third contact-pieces of the switches, and said thirdcontact-pieces being connected to the other side or branch of the line,in combination with loop-switch plugs adapted to be inserted into saidswitches and when a plug is inserted into a switch to disconnect thepair of contact-points of the switch and connect the two contact-piecesof l the plug, respectively, with said third contact-piece of the switchand with that contact-piece of the pair which is then connected with thefirst-mentioned side or branch of the line, and test receivinginstruments, one at each board, each instrument being grounded on onesideand connected on its other side to a test plug or device adapted, atthe will of the operator, to be brought into connection with any of saidthird contact-pieces at its board, substantially as set forth.

15. In a telephone-exchange system, multiple switchboards,metallic-circuit lines connected to the same, one side or branch of eachlinebeing grounded, with a transmitter-battery in its circuit at thesubscribers station when it is not in use, switches, one at eachsubscribers station with contact-points to open such ground connectionand close the two sides or branches of the line to each other when thesubscribers telephone is switched for use, and switches, one on eachboard for each line, each switch containing a pair of contact-pointsnormally in contact and a third contact-piece insulated from the rest(except by the circuit connections), said branch of the line which isnormallygrounded and has a battery in its circuit at the subscriberssta-. tion passing, successively, through the pairs of contaet-points ofthe switches of the line which are normally in contact and thence be:ing connected to said third contact-pieces of the switches, and saidthird contact-pieces being connected to the other side or branch of theline, in combination with pairs of loopswitch plugs, the twocontact-pieces of each plug being connected with the two contactpieces,respectively, of its mate by flexible switch-conductors, and each plugadapted to be inserted into said switches at its board, and when a plugis inserted into a switch to disconnect the pair of contact-points ofthe switch and connect the two contact-pieces of the plug, respectively,with said third contact-piece of the switch and with that contact-pieceof the pair which is then connected with the first-mentioned side orbranch of the line, and test receiving instruments, one at each board,each instrument being grounded on one side and connected on its otherside toa test plug or device adapted, at the will of the operator, to bebrought into connection with any of said third contact-pieces at itsboard, substantially as set forth.

' MILO G. KELLOGG.

